M4A1 Left 4 Dead

Replaces the assault rifle with a fully-automatic M4.

Just a mod of the looks and sound, the weapon functions exactly the same as before, and can work online.

Preview:

Installation requires Notepad++ (note the ++ plus plus. can also use a similar advanced text editor, hex editors).

-Place the vpk files your L4D addons folder.
REMEMBER TO BACKUP YOUR OLD FILES!

-Editing pak01_dir.vpk...
.
.REMEMBER TO BACKUP YOUR pak01_dir.vpk! YOU CAN ALWAYS GET IT BACK BY VERIFYING GAME CACHE!
.
.THESE EXACT STRINGS... NO MORE, NO LESS CHARACTERS!!!
.
.Open pak01_dir.vpk in your "...\left 4 dead    \left4dead\" folder.
.  Find:     "v_rifle"
.  Replace:  "v_rifl3"
.  (replace all 5 instances)
.
.
.  Find:     "w_rifle_m16a2"
.  Replace:  "w_rifl3_m16a2"
.  (replace all 5 instances)

-The game should now load the custom model!

-Pray Valve patches L4D to no longer require this for non-map addons!

You can also use GCFScape to extract the files and install them in their individual directories within the game (models/v_models/, materials/models/..., sound/weapons/..., etc).